Beyond perceptual load and dilution: a review of the role of working memory in selective attention

Inhibition and working memory capacity modulate the mental space-time association

This research aimed to investigate whether the mental space-time association of temporal concepts could be modulated by the availability of cognitive resources (in terms of working memory and inhibitory control capacities) and to explore whether access to this association could be an automatic process. To achieve this, two experiments were carried out. In Experiment 1, participants had to classify words with future and past meanings. The working memory load (high vs. low) was manipulated and the participants were grouped into quartiles according to their visuospatial working memory capacity (WMC). Temporal concepts were displayed subliminally (immediate masking) and supraliminally (delayed masking). The ANOVA showed a performance pattern consistent with the left-past right-future conceptual scheme, regardless of both the type of masking and the working memory load, except in high WMC participants, in which, interestingly, the space-time association effect was absent. In Experiment 2, participants were asked to respond to the colour of the font of the temporal words, and their attentional control capacity was assessed. The results indicated a timeline effect that was irrespective of the WM load and the type of perceptual processing, but not of the WM capacity or the inhibitory abilities. These findings partially endorse the automatic and implicit access to the mental space-time association and suggest the involvement of the availability of cognitive resources. Individual WMC differences appear to modulate the automatic nature of the effect rather than the processing conditions themselves.

Virtual Reality Adaptation Using Electrodermal Activity to Support the User Experience

Virtual reality is increasingly used for tasks such as work and education. Thus, rendering scenarios that do not interfere with such goals and deplete user experience are becoming progressively more relevant. We present a physiologically adaptive system that optimizes the virtual environment based on physiological arousal, i.e., electrodermal activity. We investigated the usability of the adaptive system in a simulated social virtual reality scenario. Participants completed an n-back task (primary) and a visual detection (secondary) task. Here, we adapted the visual complexity of the secondary task in the form of the number of non-player characters of the secondary task to accomplish the primary task. We show that an adaptive virtual reality can improve users’ comfort by adapting to physiological arousal regarding the task complexity. Our findings suggest that physiologically adaptive virtual reality systems can improve users’ experience in a wide range of scenarios.

Capacity limitations in template-guided multiple color search

Visual selection of target objects relies on representations of their known features in visual working memory. These representations are referred to as attentional templates. We asked how the capacity of visual working memory relates to the maximal number of attentional templates that can simultaneously guide visual selection. To measure the number of active attentional templates, we used the contingent capture paradigm where cues matching the attentional template have larger effects than cues in a non-matching color. We found larger cueing effects for matching than non-matching cues in one-, two-, and also three-color searches, suggesting that participants can establish up to three attentional templates. However, scrutiny of matching cue trials showed that with three attentional templates, larger cueing effects only occurred when the matching cue had the same color as the actual target. When the matching cue had a possible target color that was different from the actual target color, cueing effects were similar to non-matching cue colors. We assume that processing of a matching cue activates one of the three templates, which inhibits the remaining templates to the level of non-matching colors. With two colors, the inhibition from the activated template is less complete because the initial template activation is higher. Overall, only a maximum of two attentional templates can operate successfully in the contingent capture paradigm. The capacity of template-guided search is therefore far below the capacity of visual working memory.

The role of perceptual and cognitive load on inattentional blindness: A systematic review and three meta-analyses

The inattentional blindness phenomenon refers to situations in which a visible but unexpected stimulus remains consciously unnoticed by observers. This phenomenon is classically explained as the consequence of insufficient attention, because attentional resources are already engaged elsewhere or vary between individuals. However, this attentional-resources view is broad and often imprecise regarding the variety of attentional models, the different pools of resources that can be involved in attentional tasks, and the heterogeneity of the experimental paradigms. Our aim was to investigate whether a classic theoretical model of attention, namely the Load Theory, could account for a large range of empirical findings in this field by distinguishing the role of perceptual and cognitive resources in attentional selection and attentional capture by irrelevant stimuli. As this model has been mostly built on implicit measures of distractor interference, it is unclear whether its predictions also hold when explicit and subjective awareness of an unexpected stimulus is concerned. Therefore, we conducted a systematic review and meta-analyses of inattentional blindness studies investigating the role of perceptual and/or cognitive resources. The results reveal that, in line with the perceptual account of the Load Theory, inattentional blindness significantly increases with the perceptual load of the task. However, the cognitive account of this theory is not clearly supported by the empirical findings analysed here. Furthermore, the interaction between perceptual and cognitive load on inattentional blindness remains understudied. Theoretical implications for the Load Theory are discussed, notably regarding the difference between attentional capture and subjective awareness paradigms, and further research directions are provided.

EXPRESS: High Bladder Pressure Reduces the Ability to Filter Out Interference From Distractors in Low Perceptual Load Condition

According to the load theory of attention, an active cognitive control mechanism is needed to ensure that behavior is controlled by target-relevant information when distractors are also perceived. Although the active cognitive control mechanism consists of working memory, cognitive flexibility, and inhibition components, predictions regarding the load effects of this mechanism were derived mostly from studies on working memory. We aimed to test whether these predictions are also valid for an inhibition component. The inhibitory load was manipulated physiologically by creating different bladder pressure and its effects on distractor interference were examined under low and high perceptual load conditions. Results indicated that the availability of inhibitory control resources was important for decreasing the interference of distractors in the low perceptual load condition and that the high perceptual load reduced the effects of distractors independently from the availability of inhibitory resources. Results were consistent with the predictions of load theory, and to the best of our knowledge, the study provided the first piece of evidence in terms of the load effect of inhibition component on distractor interference.

The loci of Stroop effects: a critical review of methods and evidence for levels of processing contributing to color-word Stroop effects and the implications for the loci of attentional selection

Despite instructions to ignore the irrelevant word in the Stroop task, it robustly influences the time it takes to identify the color, leading to performance decrements (interference) or enhancements (facilitation). The present review addresses two questions: (1) What levels of processing contribute to Stroop effects; and (2) Where does attentional selection occur? The methods that are used in the Stroop literature to measure the candidate varieties of interference and facilitation are critically evaluated and the processing levels that contribute to Stroop effects are discussed. It is concluded that the literature does not provide clear evidence for a distinction between conflicting and facilitating representations at phonological, semantic and response levels (together referred to as informational conflict), because the methods do not currently permit their isolated measurement. In contrast, it is argued that the evidence for task conflict as being distinct from informational conflict is strong and, thus, that there are at least two loci of attentional selection in the Stroop task. Evidence suggests that task conflict occurs earlier, has a different developmental trajectory and is independently controlled which supports the notion of a separate mechanism of attentional selection. The modifying effects of response modes and evidence for Stroop effects at the level of response execution are also discussed. It is argued that multiple studies claiming to have distinguished response and semantic conflict have not done so unambiguously and that models of Stroop task performance need to be modified to more effectively account for the loci of Stroop effects.

Reduction of Pain and Spinal Nociceptive Transmission by Working Memory is Load Dependant

Working memory (WM) engagement produces pain inhibition. However, it remains unclear whether higher WM load increases this effect. The aim of this study was to investigate the interaction between WM load and pain inhibition by WM and examine the contribution of cerebrospinal mechanism. Thirty-eight healthy volunteers were assigned to one of 2 n-back groups for which WM load was different (2-back or 3-back). The experimental protocol comprised 5 counterbalanced conditions (0-back, n-back, pain, 0-back with pain, and n-back with pain). Pain and the nociceptive flexion reflex (NFR) were evoked by transcutaneous electrical stimulation of the sural nerve. Pain was significantly different between conditions, but not between n-back groups. Both the 0-back and n-back tasks reduced pain compared with pain alone, but the n-back task produced stronger pain inhibition compared with the 0-back task. NFR amplitude was significantly different between conditions but not between n-back groups. NFR was inhibited by the 0-back and n-back tasks, with no difference between the 2 tasks. These findings indicate that pain inhibition by WM is increased by WM load, but only to a certain point. NFR inhibition by WM suggests that inhibition of pain by WM depends, at least in part, on cerebrospinal mechanism. PERSPECTIVE: This behavioral and electrophysiological study shows that engaging in a cognitive task reduces pain by decreasing spinal nociceptive transmission, depending on task difficulty. These findings may yield better nonpharmacological pain therapies based on individual differences in working memory performance and capacity as well as several factors that regulate working memory.

Individual Differences in Working Memory and the N2pc

The lateralized ERP N2pc component has been shown to be an effective marker of attentional object selection when elicited in a visual search task, specifically reflecting the selection of a target item among distractors. Moreover, when targets are known in advance, the visual search process is guided by representations of target features held in working memory at the time of search, thus guiding attention to objects with target-matching features. Previous studies have shown that manipulating working memory availability via concurrent tasks or within task manipulations influences visual search performance and the N2pc. Other studies have indicated that visual (non-spatial) vs. spatial working memory manipulations have differential contributions to visual search. To investigate this the current study assesses participants' visual and spatial working memory ability independent of the visual search task to determine whether such individual differences in working memory affect task performance and the N2pc. Participants (n = 205) completed a visual search task to elicit the N2pc and separate visual working memory (VWM) and spatial working memory (SPWM) assessments. Greater SPWM, but not VWM, ability is correlated with and predicts higher visual search accuracy and greater N2pc amplitudes. Neither VWM nor SPWM was related to N2pc latency. These results provide additional support to prior behavioral and neural visual search findings that spatial WM availability, whether as an ability of the participant's processing system or based on task demands, plays an important role in efficient visual search.

Working memory capacity modulates expectancy-based strategic processing: Behavioral and electrophysiological evidence

The present research measured participants' event-related brain activity while they performed a Stroop-priming task that induced the implementation of expectancy-based strategic processes. Participants identified a colored (red vs. green) target patch preceded by a prime word (GREEN or RED), with incongruent prime-target pairings being more frequent (75 %) than congruent pairs (25 %). The prime-target stimulus onset asynchrony (SOA) was manipulated at two levels: 300 vs. 700 ms. Participants also performed a change localization task to assess their working memory capacity (WMC). At the 300 ms SOA, all participants presented a Stroop-priming congruency effect (slower responses on incongruent than on congruent trials) and an increased N2 amplitude in incongruent trials, irrespective of their WMC. At the 700-ms SOA, the lower-WMC group showed again a larger negative-going waveform to incongruent targets, whereas the higher-WMC group exhibited a reversed Stroop-priming congruency effect (faster responses to incongruent targets) and the N2 component was absent.

The interaction between language and working memory: a systematic review of fMRI studies in the past two decades

Language processing involves other cognitive domains, including Working Memory (WM). Much detail about the neural correlates of language and WM interaction remains unclear. This review summarizes the evidence for the interaction between WM and language obtained via functional Magnetic Resonance Imaging (fMRI) in the past two decades. The search was limited to PubMed, Google Scholar, Science direct and Neurosynth for working memory, language, fMRI, neuroimaging, cognition, attention, network, connectome keywords. The exclusion criteria consisted of studies including children, older adults, bilingual or multilingual population, clinical cases, music, sign language, speech, motor processing, review papers, meta-analyses, electroencephalography/event-related potential, and positron emission tomography. A total of 20 articles were included and discussed in four categories: language comprehension, language production, syntax, and networks. Studies on neural correlates of WM and language interaction are rare. Language tasks that involve WM activate common neural systems. Activated areas can be associated with cognitive concepts proposed by Baddeley and Hitch (1974), including the phonological loop of WM (mainly Broca and Wernicke's areas), other prefrontal cortex and right hemispheric regions linked to the visuospatial sketchpad. There is a clear, dynamic interaction between language and WM, reflected in the involvement of subcortical structures, particularly the basal ganglia (caudate), and of widespread right hemispheric regions. WM involvement is levered by cognitive demand in response to task complexity. High WM capacity readers draw upon buffer memory systems in midline cortical areas to decrease the WM demands for efficiency. Different dynamic networks are involved in WM and language interaction in response to the task in hand for an ultimate brain function efficiency, modulated by language modality and attention.

Visual and verbal working memory loads interfere with scene-viewing

Working memory is thought to be divided into distinct visual and verbal subsystems. Studies of visual working memory frequently use verbal working memory tasks as control conditions and/or use articulatory suppression to ensure that visual load is not transferred to verbal working memory. Using these verbal tasks relies on the assumption that the verbal working memory load will not interfere with the same processes as visual working memory. In the present study, participants maintained a visual or verbal working memory load as they simultaneously viewed scenes while their eye movements were recorded. Because eye movements and visual working memory are closely linked, we anticipated the visual load would interfere with scene-viewing (and vice versa), while the verbal load would not. Surprisingly, both visual and verbal memory loads interfered with scene-viewing behavior, while eye movements during scene-viewing did not significantly interfere with performance on either memory task. These results suggest that a verbal working memory load can interfere with eye movements in a visual task.

Eye behavior predicts susceptibility to visual distraction during internally directed cognition

When we engage in internally directed cognition (e.g., planning or imagination), our eye behavior decouples from external stimuli and couples to internal representations (e.g., internal visualizations of ideas). Here, we investigated whether eye behavior predicts the susceptibility to visual distraction during internally directed cognition. To this end, participants performed a divergent thinking task, which required internally directed attention, and we measured distraction in terms of attention capture by unrelated images. We used multilevel mixed models to predict visual distraction by eye behavior right before distractor onset. In Study 1 (N = 38), visual distraction was predicted by increased saccade and blink rate, and higher pupil dilation. We replicated these findings in Study 2 using the same task, but with less predictable distractor onsets and a larger sample (N = 144). We also explored whether individual differences in susceptibility to visual distraction were related to cognitive ability and task performance. Taken together, variation in eye behavior was found to be a consistent predictor of visual distraction during internally directed cognition. This highlights the relevance of eye parameters as objective indicators of internal versus external attentional focus and distractibility during complex mental tasks.

Composite Face Effect Predicts Configural Encoding in Visual Short-Term Memory

In natural vision, visual scenes consist of individual items (e.g., trees) and global properties of items as a whole (e.g., forest). These different levels of representations can all contribute to perception, natural scene understanding, sensory memory, working memory, and long-term memory. Despite these various hierarchical representations across perception and cognition, the nature of the global representations has received considerably less attention in empirical research on working memory than item representations. The present study aimed to understand the perceptual root of the configural information retained in Visual Short-term Memory (VSTM). Specifically, we assessed whether configural VSTM was related to holistic face processing across participants using an individual differences approach. Configural versus item encoding in VSTM was assessed using Xie and Zhang’s (2017) dual-trace Signal Detection Theory model in a change detection task for orientation. Configural face processing was assessed using Le Grand composite face effect (CFE). In addition, overall face recognition was assessed using Glasgow Face Matching Test (GFMT). Across participants, holistic face encoding, but not face recognition accuracy, predicted configural information, but not item information, retained in VSTM. Together, these findings suggest that configural encoding in VSTM may have a perceptual root.

Executive functions

First, executive functions are defined. Then the development of executive functions in children, from infancy to 10-11 years of age, is briefly described. The relation between the speed of processing and the development of executive functions is addressed. Finally, tools and pointers for evaluating executive functioning in younger and older children are discussed. A cautionary note is sounded, in that almost no executive function measure requires only one executive function. A child might fail a working memory task because of problems with inhibitory control (not working memory), fail an inhibitory control task because of working memory problems, or fail a cognitive flexibility, planning, or reasoning task because of problems with inhibitory control or working memory.

Capture and Control: Working Memory Modulates Attentional Capture by Reward-Related Stimuli

Physically salient but task-irrelevant distractors can capture attention in visual search, but resource-dependent, executive-control processes can help reduce this distraction. However, it is not only physically salient stimuli that grab our attention: Recent research has shown that reward history also influences the likelihood that stimuli will capture attention. Here, we investigated whether resource-dependent control processes modulate the effect of reward on attentional capture, much as for the effect of physical salience. To this end, we used eye tracking with a rewarded visual search task and compared performance under conditions of high and low working memory load. In two experiments, we demonstrated that oculomotor capture by high-reward distractor stimuli is enhanced under high memory load. These results highlight the role of executive-control processes in modulating distraction by reward-related stimuli. Our findings have implications for understanding the neurocognitive processes involved in real-life conditions in which reward-related stimuli may influence behavior, such as addiction.

Modulation of parafoveal word processing by cognitive load during modified visual search tasks

During visual search for simple items, the amount of information that can be processed in parafoveal vision depends on the cognitive resources that are available. However, whether this applies to the semantic processing of words remains controversial. This work was designed to manipulate simultaneously two sources of cognitive load to study their impact on the depth of parafoveal word processing during a modified visual search task. The participants had to search for target words among parafoveally presented semantic, orthographic or target-unrelated distractor words while their electroencephalogram was recorded. The task-related load was manipulated by either giving target words in advance (literal task) or giving only a semantic clue to define them (categorical task). The foveal load was manipulated by displaying either a word or hash symbols at the centre of the screen. Parafoveal orthographic and semantic distractors had an impact on the early event-related potential component P2a only in the literal task and when hash symbols were displayed at the fovea, i.e., when both the task-related and foveal loads were low. The data show that all sources of cognitive load must be considered to understand how parafoveal words are processed in visual search contexts.

Pupil size and search performance in low and high perceptual load

The ability to focus on a task while disregarding irrelevant information is an example of selective attention. The perceptual-load hypothesis argues that the occurrence of early or late selection mechanisms is determined by task-relevant perceptual load. Additionally, evidence shows that pupil size serves as proxy of locus coeruleus-norepinephrine (LC-NE) activity, a system associated with cognitive and attentional mediation. Here, we assessed pupil baseline (and pupil dilation) as predictors of load-related early and late selection performance. Participants were asked to search for a target in conditions of high and low perceptual load, while ignoring irrelevant stimuli. The results showed that pupil baseline size, measured prior trial onset, significantly predicted the upcoming search efficiency only in low perceptual load, when-according to the perceptual-load hypothesis-all perceptual information receives attentional resources. In addition, pupil dilation was linked to the time course of perceptual processing and predicted response times in both perceptual load conditions, an association that was enhanced in high load. Thus, this study relates attentional selection mechanisms, as defined by the perceptual-load theory, with pupil-related LC-NE activity. Because pupil baseline predicted attentional performance in low load but not in high load, this suggests that different attentional mechanisms are involved, one in which the LC-NE system plays a key role (low load) and one in which it is less relevant (high load). This suggests that the degree with which LC-NE influences behavioral performance is related to the perceptual load of the task at hand.

Expectancy-Based Strategic Processes Are Influenced by Spatial Working Memory Load and Individual Differences in Working Memory Capacity

The present research examined whether imposing a high (or low) working memory (WM) load in different types of non-verbal WM tasks could affect the implementation of expectancy-based strategic processes in a sequential verbal Stroop task. Participants had to identify a colored (green vs. red) target patch that was preceded by a prime word (GREEN or RED), which was either incongruent or congruent with the target color on 80% and 20% of the trials, respectively. Previous findings have shown that participants can strategically use this information to predict the upcoming target color, and avoid the standard Stroop interference effect. The Stroop task was combined with different types of non-verbal WM tasks. In Experiment 1, participants had to retain sets of four arrows that pointed either in the same (low WM load) or in different directions (high WM load). In Experiment 2, they had to remember the spatial locations of four dots which either formed a straight line (low load) or were randomly scattered in a square grid (high load). In addition, participants in the two experiments performed a change localization task to assess their WM capacity (WMC). The results in both experiments showed a reliable congruency by WM load interaction. When the Stroop task was performed under a high WM load, participants were unable to efficiently ignore the incongruence of the prime, as they consistently showed a standard Stroop effect, regardless of their WMC. Under a low WM load, however, a strategically dependent effect (reversed Stroop) emerged. This ability to ignore the incongruence of the prime was modulated by WMC, such that the reversed Stroop effect was mainly found in higher WMC participants. The findings that expectancy-based strategies on a verbal Stroop task are modulated by load on different types of spatial WM tasks point at a domain-general effect of WM on strategic processing. The present results also suggest that the impact of loading WM on expectancy-based strategies can be modulated by individual differences in WMC.

Impact of Spatial and Verbal Short-Term Memory Load on Auditory Spatial Attention Gradients

Short-term memory load can impair attentional control, but prior work shows that the extent of the effect ranges from being very general to very specific. One factor for the mixed results may be reliance on point estimates of memory load effects on attention. Here we used auditory attention gradients as an analog measure to map-out the impact of short-term memory load over space. Verbal or spatial information was maintained during an auditory spatial attention task and compared to no-load. Stimuli were presented from five virtual locations in the frontal azimuth plane, and subjects focused on the midline. Reaction times progressively increased for lateral stimuli, indicating an attention gradient. Spatial load further slowed responses at lateral locations, particularly in the left hemispace, but had little effect at midline. Verbal memory load had no (Experiment 1), or a minimal (Experiment 2) influence on reaction times. Spatial and verbal load increased switch costs between memory encoding and attention tasks relative to the no load condition. The findings show that short-term memory influences the distribution of auditory attention over space; and that the specific pattern depends on the type of information in short-term memory.

To hear or not to hear: Voice processing under visual load

Adaptation to female voices causes subsequent voices to be perceived as more male, and vice versa. This contrastive aftereffect disappears under spatial inattention to adaptors, suggesting that voices are not encoded automatically. According to Lavie, Hirst, de Fockert, and Viding (2004), the processing of task-irrelevant stimuli during selective attention depends on perceptual resources and working memory. Possibly due to their social significance, faces may be an exceptional domain: That is, task-irrelevant faces can escape perceptual load effects. Here we tested voice processing, to study whether voice gender aftereffects (VGAEs) depend on low or high perceptual (Exp. 1) or working memory (Exp. 2) load in a relevant visual task. Participants adapted to irrelevant voices while either searching digit displays for a target (Exp. 1) or recognizing studied digits (Exp. 2). We found that the VGAE was unaffected by perceptual load, indicating that task-irrelevant voices, like faces, can also escape perceptual-load effects. Intriguingly, the VGAE was increased under high memory load. Therefore, visual working memory load, but not general perceptual load, determines the processing of task-irrelevant voices.

Behavioral and Neural Correlates of Executive Function: Interplay between Inhibition and Updating Processes

This study investigated the interaction between two executive function processes, inhibition and updating, through analyses of behavioral, neurophysiological, and effective connectivity metrics. Although, many studies have focused on behavioral effects of executive function processes individually, few studies have examined the dynamic causal interactions between these two functions. A total of twenty participants from a local university performed a dual task combing flanker and n-back experimental paradigms, and completed the Operation Span Task designed to measure working memory capacity. We found that both behavioral (accuracy and reaction time) and neurophysiological (P300 amplitude and alpha band power) metrics on the inhibition task (i.e., flanker task) were influenced by the updating load (n-back level) and modulated by working memory capacity. Using independent component analysis, source localization (DIPFIT), and Granger Causality analysis of the EEG time-series data, the present study demonstrated that manipulation of cognitive demand in a dual executive function task influenced the causal neural network. We compared connectivity across three updating loads (n-back levels) and found that experimental manipulation of working memory load enhanced causal connectivity of a large-scale neurocognitive network. This network contains the prefrontal and parietal cortices, which are associated with inhibition and updating executive function processes. This study has potential applications in human performance modeling and assessment of mental workload, such as the design of training materials and interfaces for those performing complex multitasking under stress.

Large inter-individual and intra-individual variability in the effect of perceptual load

This study examined whether the recurrent difficulty to replicate results obtained with paradigms measuring distractor processing as a function of perceptual load is due to individual differences. We first reanalyzed, at the individual level, the data of eight previously reported experiments. These reanalyses revealed substantial inter-individual differences, with particularly low percentage of participants whose performance matched the load theory's predictions (i.e., larger distractor interference with low than high levels of load). Moreover, frequently the results were opposite to the theory's predictions-larger interference in the high than low load condition; and often a reversed compatibility effect emerged-better performance in the incompatible than neutral condition. Subsequently, seven observers participated in five identical experimental sessions. If the observed inter-individual differences are due to some stable trait or perceptual capacity, similar results should have emerged in all sessions of a given participant. However, all seven participants showed large between-sessions variations with similar patterns to those found between participants. These findings question the theoretical foundation implemented with these paradigms, as none of the theories suggested thus far can account for such inter- and intra-individual differences. Thus, these paradigms should be used with caution until further research will provide better understanding of what they actually measure.

The Influence of Working Memory Load on Expectancy-Based Strategic Processes in the Stroop-Priming Task

The present study investigated whether a differential availability of cognitive control resources as a result of varying working memory (WM) load could affect the capacity for expectancy-based strategic actions. Participants performed a Stroop-priming task in which a prime word (GREEN or RED) was followed by a colored target (red vs. green) that participants had to identify. The prime was incongruent or congruent with the target color on 80 and 20% of the trials, respectively, and participants were informed about the differential proportion of congruent vs. incongruent trials. This task was interleaved with a WM task, such that the prime word was preceded by a sequence of either a same digit repeated five times (low load) or five different random digits (high load), which should be retained by participants. After two, three, or four Stroop trials, they had to decide whether or not a probe digit was a part of the memory set. The key finding was a significant interaction between prime-target congruency and WM load: Whereas a strategy-dependent (reversed Stroop) effect was found under low WM load, a standard Stroop interference effect was observed under high WM load. These findings demonstrate that the availability of WM is crucial for implementing expectancy-based strategic actions.

Effects of working memory contents and perceptual load on distractor processing: When a response-related distractor is held in working memory

Working memory and attention are closely related. Recent research has shown that working memory can be viewed as internally directed attention. Working memory can affect attention in at least two ways. One is the effect of working memory load on attention, and the other is the effect of working memory contents on attention. In the present study, an interaction between working memory contents and perceptual load in distractor processing was investigated. Participants performed a perceptual load task in a standard form in one condition (Single task). In the other condition, a response-related distractor was maintained in working memory, rather than presented in the same stimulus display as a target (Dual task). For the Dual task condition, a significant compatibility effect was found under high perceptual load; however, there was no compatibility effect under low perceptual load. These results suggest that the way the contents of working memory affect visual search depends on perceptual load.

The Role of Cognitive Load in Intentional Forgetting Using the Think/No-Think Task

Abstract. We investigated the role of cognitive control in intentional forgetting by manipulating working memory load during the think/no-think task. In two experiments, participants learned a series of cue-target word pairs and were asked to recall the target words associated with some cues or to avoid thinking about the target associated with other cues. In addition to this, participants also performed a modified version of the n-back task which required them to respond to the identity of a single target letter present in the currently presented cue word (n = 0 condition, low working memory load), and in either the previous cue word (n = 1 condition, high working memory load, Experiment 1) or the cue word presented two trials previously (n = 2 condition, high working memory load, Experiment 2). Participants’ memory for the target words was subsequently tested using same and novel independent probes. In both experiments it was found that although participants were successful at forgetting on both the same and independent-probe tests in the low working memory load condition, they were only successful at forgetting on the same-probe test in the high working memory load condition. We argue that our findings suggest that the high load working memory task diverted attention from direct suppression and acted as an interference-based strategy. Thus, when cognitive resources are limited participants can switch between the strategies they use to prevent unwanted memories from coming to mind.

Individual Differences in Working Memory Capacity Modulates Semantic Negative Priming from Single Prime Words

The present study investigated whether semantic negative priming from single prime words depends on the availability of cognitive control resources. Participants with high vs. low working memory capacity (as assessed by their performance in complex span and attentional control tasks) were instructed to either attend to or ignore a briefly presented single prime word that was followed by either a semantically related or unrelated target word on which participants made a lexical decision. Individual differences in working memory capacity (WMC) mainly affected the processing of the ignored primes, but not the processing of the attended primes: While the latter produced reliable positive semantic priming for both high- and low-WMC participants, the former gave rise to reliable semantic negative priming only for high WMC participants, with low WMC participants showing the opposite positive priming effect. The present results extend previous findings in demonstrating that (a) single negative priming can reliably generalize to semantic associates of the prime words, and (b) a differential availability of cognitive control resources can reliably modulate the negative priming effect at a semantic level of representation.

Increasing Working Memory Load Reduces Processing of Cross-Modal Task-Irrelevant Stimuli Even after Controlling for Task Difficulty and Executive Capacity

The classic account of the load theory (LT) of attention suggests that increasing cognitive load leads to greater processing of task-irrelevant stimuli due to competition for limited executive resource that reduces the ability to actively maintain current processing priorities. Studies testing this hypothesis have yielded widely divergent outcomes. The inconsistent results may, in part, be related to variability in executive capacity (EC) and task difficulty across subjects in different studies. Here, we used a cross-modal paradigm to investigate whether augmented working memory (WM) load leads to increased early distracter processing, and controlled for the potential confounders of EC and task difficulty. Twenty-three young subjects were engaged in a primary visual WM task, under high and low load conditions, while instructed to ignore irrelevant auditory stimuli. Demands of the high load condition were individually titrated to make task difficulty comparable across subjects with differing EC. Event-related potentials (ERPs) were used to measure neural activity in response to stimuli presented in both the task relevant modality (visual) and task-irrelevant modality (auditory). Behavioral results indicate that the load manipulation and titration procedure of the primary visual task were successful. ERPs demonstrated that in response to visual target stimuli, there was a load-related increase in the posterior slow wave, an index of sustained attention and effort. Importantly, under high load, there was a decrease of the auditory N1 in response to distracters, a marker of early auditory processing. These results suggest that increased WM load is associated with enhanced attentional engagement and protection from distraction in a cross-modal setting, even after controlling for task difficulty and EC. Our findings challenge the classic LT and offer support for alternative models.

Effects of cognitive load on neural and behavioral responses to smoking-cue distractors

Smoking cessation failures are frequently thought to reflect poor top-down regulatory control over behavior. Previous studies have suggested that smoking cues occupy limited working memory resources, an effect that may contribute to difficulty achieving abstinence. Few studies have evaluated the effects of cognitive load on the ability to actively maintain information in the face of distracting smoking cues. For the present study, we adapted an fMRI probed recall task under low and high cognitive load with three distractor conditions: control, neutral images, or smoking-related images. Consistent with a limited-resource model of cue reactivity, we predicted that the performance of daily smokers (n = 17) would be most impaired when high load was paired with smoking distractors. The results demonstrated a main effect of load, with decreased accuracy under high, as compared to low, cognitive load. Surprisingly, an interaction revealed that the effect of load was weakest in the smoking cue distractor condition. Along with this behavioral effect, we observed significantly greater activation of the right inferior frontal gyrus (rIFG) in the low-load condition than in the high-load condition for trials containing smoking cue distractors. Furthermore, load-related changes in rIFG activation partially mediated the effects of load on task accuracy in the smoking-cue distractor condition. These findings are discussed in the context of prevailing cognitive and cue reactivity theories. These results suggest that high cognitive load does not necessarily make smokers more susceptible to interference from smoking-related stimuli, and that elevated load may even have a buffering effect in the presence of smoking cues under certain conditions.

Modeling the Effects of Perceptual Load: Saliency, Competitive Interactions, and Top-Down Biases

A computational model of visual selective attention has been implemented to account for experimental findings on the Perceptual Load Theory (PLT) of attention. The model was designed based on existing neurophysiological findings on attentional processes with the objective to offer an explicit and biologically plausible formulation of PLT. Simulation results verified that the proposed model is capable of capturing the basic pattern of results that support the PLT as well as findings that are considered contradictory to the theory. Importantly, the model is able to reproduce the behavioral results from a dilution experiment, providing thus a way to reconcile PLT with the competing Dilution account. Overall, the model presents a novel account for explaining PLT effects on the basis of the low-level competitive interactions among neurons that represent visual input and the top-down signals that modulate neural activity. The implications of the model concerning the debate on the locus of selective attention as well as the origins of distractor interference in visual displays of varying load are discussed.

Visual short-term memory load strengthens selective attention

Perceptual load theory accounts for many attentional phenomena; however, its mechanism remains elusive because it invokes underspecified attentional resources. Recent dual-task evidence has revealed that a concurrent visual short-term memory (VSTM) load slows visual search and reduces contrast sensitivity, but it is unknown whether a VSTM load also constricts attention in a canonical perceptual load task. If attentional selection draws upon VSTM resources, then distraction effects-which measure attentional "spill-over"-will be reduced as competition for resources increases. Observers performed a low perceptual load flanker task during the delay period of a VSTM change detection task. We observed a reduction of the flanker effect in the perceptual load task as a function of increasing concurrent VSTM load. These findings were not due to perceptual-level interactions between the physical displays of the two tasks. Our findings suggest that perceptual representations of distractor stimuli compete with the maintenance of visual representations held in memory. We conclude that access to VSTM determines the degree of attentional selectivity; when VSTM is not completely taxed, it is more likely for task-irrelevant items to be consolidated and, consequently, affect responses. The "resources" hypothesized by load theory are at least partly mnemonic in nature, due to the strong correspondence they share with VSTM capacity.

Interactions Between Modality of Working Memory Load and Perceptual Load in Distractor Processing

The present study investigated interactions between working memory load and perceptual load. The load theory (Lavie, Hirst, de Fockert, & Viding, 2004 ) claims that perceptual load decreases distractor interference, whereas working memory load increases interference. However, recent studies showed that effects of working memory might depend on the relationship between modalities of working memory and task stimuli. Here, we examined whether the relationship between working memory load and perceptual load would remain the same across modalities. The results of Experiment 1 showed that verbal working memory load did not affect a compatibility effect for low perceptual load, whereas it increased the compatibility effect for high perceptual load. In Experiment 2, the compatibility effect remained the same regardless of visual working memory load. These results suggest that the effects of working memory load and perceptual load depend on the relationship between the modalities of working memory and stimuli.

A Neurophysiological and Neuropsychological Consideration of Mindful Movement: Clinical and Research Implications

In this article, we present ideas related to three key aspects of mindfulness training: the regulation of attention via noradrenaline, the importance of working memory and its various components (particularly the central executive and episodic buffer), and the relationship of both of these to mind-wandering. These same aspects of mindfulness training are also involved in the preparation and execution of movement and implicated in the pathophysiology of psychosis. We argue that by moving in a mindful way, there may be an additive effect of training as the two elements of the practice (mindfulness and movement) independently, and perhaps synergistically, engage common underlying systems (the default mode network). We discuss how working with mindful movement may be one route to mindfulness training for individuals who would struggle to sit still to complete the more commonly taught mindfulness practices. Drawing on our clinical experience working with individuals with severe and enduring mental health conditions, we show the real world application of these ideas and how they can be used to help those who are suffering and for whom current treatments are still far from adequate.

Costs of switching auditory spatial attention in following conversational turn-taking

Following a multi-talker conversation relies on the ability to rapidly and efficiently shift the focus of spatial attention from one talker to another. The current study investigated the listening costs associated with shifts in spatial attention during conversational turn-taking in 16 normally-hearing listeners using a novel sentence recall task. Three pairs of syntactically fixed but semantically unpredictable matrix sentences, recorded from a single male talker, were presented concurrently through an array of three loudspeakers (directly ahead and +/−30° azimuth). Subjects attended to one spatial location, cued by a tone, and followed the target conversation from one sentence to the next using the call-sign at the beginning of each sentence. Subjects were required to report the last three words of each sentence (speech recall task) or answer multiple choice questions related to the target material (speech comprehension task). The reading span test, attention network test, and trail making test were also administered to assess working memory, attentional control, and executive function. There was a 10.7 ± 1.3% decrease in word recall, a pronounced primacy effect, and a rise in masker confusion errors and word omissions when the target switched location between sentences. Switching costs were independent of the location, direction, and angular size of the spatial shift but did appear to be load dependent and only significant for complex questions requiring multiple cognitive operations. Reading span scores were positively correlated with total words recalled, and negatively correlated with switching costs and word omissions. Task switching speed (Trail-B time) was also significantly correlated with recall accuracy. Overall, this study highlights (i) the listening costs associated with shifts in spatial attention and (ii) the important role of working memory in maintaining goal relevant information and extracting meaning from dynamic multi-talker conversations.

A parietal biomarker for ADHD liability: as predicted by the distributed effects perspective model of ADHD

BACKGROUND

We previously hypothesized that poor task-directed sensory information processing should be indexed by increased weighting of right hemisphere (RH) biased attention and visuo-perceptual brain functions during task operations and have demonstrated this phenotype in ADHD across multiple studies, using multiple methodologies. However, in our recent distributed effects model of ADHD, we surmised that this phenotype is not ADHD specific, but rather more broadly reflective of any circumstance that disrupts the induction and maintenance of an emergent task-directed neural architecture. Under this view, increased weighting of RH-biased attention and visuo-perceptual brain functions is expected to generally index neurocognitive sets that are not optimized for task-directed thought and action, and when durable expressed, liability for ADHD.

METHOD

The current study tested this view by examining whether previously identified rightward parietal EEG asymmetry in ADHD was associated with common ADHD characteristics and comorbidities [i.e., ADHD risk factors (RFs)].

RESULTS

Barring one exception (non-right handedness), we found that it was. Rightward parietal asymmetry (RPA) was associated with carrying the DRD4-7R risk allele, being male, having mood disorder, and having anxiety disorder. However, differences in the specific expression of RPA were observed, which are discussed in relation to possible unique mechanisms underlying ADHD liability in different ADHD RFs.

CONCLUSION

Rightward parietal asymmetry appears to be a durable feature of ADHD liability, as predicted by the Distributed Effects Perspective Model of ADHD. Moreover, variability in the expression of this phenotype may shed light on different sources of ADHD liability.

Looking and touching: what extant approaches reveal about the structure of early word knowledge

The goal of the current study is to assess the temporal dynamics of vision and action to evaluate the underlying word representations that guide infants' responses. Sixteen-month-old infants participated in a two-alternative forced-choice word-picture matching task. We conducted a moment-by-moment analysis of looking and reaching behaviors as they occurred in tandem to assess the speed with which a prompted word was processed (visual reaction time) as a function of the type of haptic response: Target, Distractor, or No Touch. Visual reaction times (visual RTs) were significantly slower during No Touches compared to Distractor and Target Touches, which were statistically indistinguishable. The finding that visual RTs were significantly faster during Distractor Touches compared to No Touches suggests that incorrect and absent haptic responses appear to index distinct knowledge states: incorrect responses are associated with partial knowledge whereas absent responses appear to reflect a true failure to map lexical items to their target referents. Further, we found that those children who were faster at processing words were also those children who exhibited better haptic performance. This research provides a methodological clarification on knowledge measured by the visual and haptic modalities and new evidence for a continuum of word knowledge in the second year of life.

Abnormal Parietal Brain Function in ADHD: Replication and Extension of Previous EEG Beta Asymmetry Findings

BACKGROUND

Abundant work indicates ADHD abnormal posterior brain structure and function, including abnormal structural and functional asymmetries and reduced corpus callosum size. However, this literature has attracted considerably less research interest than fronto-striatal findings.

OBJECTIVE

To help address this imbalance, the current study replicates and extends our previous work showing abnormal parietal brain function in ADHD adults during the Conner's Continuous Performance Test (CPT).

METHOD

Our previous study found that ADHD adults had increased rightward EEG beta (16-21 Hz) asymmetry in inferior parietal brain regions during the CPT (p = 0.00001), and that this metric exhibited a lack of normal correlation (i.e., observed in controls) with beta asymmetry at temporal-parietal regions. We re-tested these effects in a new ADHD sample and with both new and old samples combined. We additionally examined: (a) EEG asymmetry in multiple frequency bands, (b) unilateral effects for all asymmetry findings, and (c) the association between EEG asymmetry and a battery of cognitive tests.

RESULTS

We replicated our original findings by demonstrating abnormal rightward inferior parietal beta asymmetry in adults with ADHD during the CPT, and again this metric exhibited abnormal reduced correlation to temporal-parietal beta asymmetry. Novel analyses also demonstrated a broader pattern of rightward beta and theta asymmetry across inferior, superior, and temporal-parietal brain regions, and showed that rightward parietal asymmetry in ADHD was atypically associated with multiple cognitive tests.

CONCLUSION

Abnormal increased rightward parietal EEG beta asymmetry is an important feature of ADHD. We speculate that this phenotype may occur with any form of impaired capacity for top-down task-directed control over sensory encoding functions, and that it may reflect associated increase of attentional shifting and compensatory sustained/selective attention.

Neural effects of cognitive control load on auditory selective attention

Whether and how working memory disrupts or alters auditory selective attention is unclear. We compared simultaneous event-related potentials (ERP) and functional magnetic resonance imaging (fMRI) responses associated with task-irrelevant sounds across high and low working memory load in a dichotic-listening paradigm. Participants performed n-back tasks (1-back, 2-back) in one ear (Attend ear) while ignoring task-irrelevant speech sounds in the other ear (Ignore ear). The effects of working memory load on selective attention were observed at 130-210ms, with higher load resulting in greater irrelevant syllable-related activation in localizer-defined regions in auditory cortex. The interaction between memory load and presence of irrelevant information revealed stronger activations primarily in frontal and parietal areas due to presence of irrelevant information in the higher memory load. Joint independent component analysis of ERP and fMRI data revealed that the ERP component in the N1 time-range is associated with activity in superior temporal gyrus and medial prefrontal cortex. These results demonstrate a dynamic relationship between working memory load and auditory selective attention, in agreement with the load model of attention and the idea of common neural resources for memory and attention.

Domain-specific control of selective attention

Previous research has shown that loading information on working memory affects selective attention. However, whether the load effect on selective attention is domain-general or domain-specific remains unresolved. The domain-general effect refers to the findings that load in one content (e.g. phonological) domain in working memory influences processing in another content (e.g., visuospatial) domain. Attentional control supervises selection regardless of information domain. The domain-specific effect refers to the constraint of influence only when maintenance and processing operate in the same domain. Selective attention operates in a specific content domain. This study is designed to resolve this controversy. Across three experiments, we manipulated the type of representation maintained in working memory and the type of representation upon which the participants must exert control to resolve conflict and select a target into the focus of attention. In Experiments 1a and 1b, participants maintained digits and nonverbalized objects, respectively, in working memory while selecting a target in a letter array. In Experiment 2, we presented auditory digits with a letter flanker task to exclude the involvement of resource competition within the same input modality. In Experiments 3a and 3b, we replaced the letter flanker task with an object flanker task while manipulating the memory load on object and digit representation, respectively. The results consistently showed that memory load modulated distractibility only when the stimuli of the two tasks were represented in the same domain. The magnitude of distractor interference was larger under high load than under low load, reflecting a lower efficacy of information prioritization. When the stimuli of the two tasks were represented in different domains, memory load did not modulate distractibility. Control of processing priority in selective attention demands domain-specific resources.

Individual differences in distractibility: An update and a model

This paper reviews the current literature on individual differences in susceptibility to the effects of background sound on visual-verbal task performance. A large body of evidence suggests that individual differences in working memory capacity (WMC) underpin individual differences in susceptibility to auditory distraction in most tasks and contexts. Specifically, high WMC is associated with a more steadfast locus of attention (thus overruling the call for attention that background noise may evoke) and a more constrained auditory-sensory gating (i.e., less processing of the background sound). The relation between WMC and distractibility is a general framework that may also explain distractibility differences between populations that differ along variables that covary with WMC (such as age, developmental disorders, and personality traits). A neurocognitive task-engagement/distraction trade-off (TEDTOFF) model that summarizes current knowledge is outlined and directions for future research are proposed.

Visual Network Asymmetry and Default Mode Network Function in ADHD: An fMRI Study

BACKGROUND

A growing body of research has identified abnormal visual information processing in attention-deficit hyperactivity disorder (ADHD). In particular, slow processing speed and increased reliance on visuo-perceptual strategies have become evident.

OBJECTIVE

The current study used recently developed fMRI methods to replicate and further examine abnormal rightward biased visual information processing in ADHD and to further characterize the nature of this effect; we tested its association with several large-scale distributed network systems.

METHOD

We examined fMRI BOLD response during letter and location judgment tasks, and directly assessed visual network asymmetry and its association with large-scale networks using both a voxelwise and an averaged signal approach.

RESULTS

Initial within-group analyses revealed a pattern of left-lateralized visual cortical activity in controls but right-lateralized visual cortical activity in ADHD children. Direct analyses of visual network asymmetry confirmed atypical rightward bias in ADHD children compared to controls. This ADHD characteristic was atypically associated with reduced activation across several extra-visual networks, including the default mode network (DMN). We also found atypical associations between DMN activation and ADHD subjects' inattentive symptoms and task performance.

CONCLUSION

The current study demonstrated rightward VNA in ADHD during a simple letter discrimination task. This result adds an important novel consideration to the growing literature identifying abnormal visual processing in ADHD. We postulate that this characteristic reflects greater perceptual engagement of task-extraneous content, and that it may be a basic feature of less efficient top-down task-directed control over visual processing. We additionally argue that abnormal DMN function may contribute to this characteristic.

A distributed effects perspective of dimensionally defined psychiatric disorders: and convergent versus core deficit effects in ADHD

The focus of psychiatric and psychological research has arguably shifted from brain damage and psychosis to more common forms of psychopathology that reflect extremes variants of otherwise normal cognitive and behavioral characteristics. Now, in addition to trying to understand overtly damaged brain-function (flat tire effects), we are also seeking to understand liabilities associated with non-optimized, but otherwise intact, cognitive and behavioral abilities (poor tuning effects). This shift has pushed us to evolve our investigational strategies to more broadly consider whole-brain integrated brain systems, as well as seek to develop more specific quantifiable indicators of impoverished brain function and behavior. This paper discusses such challenges in relation to dimensionally defined psychiatric disorders and presents a novel whole-brain integrated perspective of ADHD brain function pathology.